First of all, olefin resins such as polyethylene, polypropylene and polybutene-1 have advantages in their excellent moldability, heat resistance, mechanical properties, low specific gravity and the like and are, therefore, widely utilized in films, sheets and various molded articles (such as structural components). However, since olefin resins have a slow crystallization rate after being heat-molded, not only there are such problems that the molding cycle in processing is long, but also there are cases where the resulting molded article is deformed due to crystallization that progresses even after molding. Moreover, since olefin resins generate large crystals when heat-molded, there are such drawbacks that the resulting molded article has insufficient strength and poor transparency.
It is known, however, that these drawbacks are attributed to the crystallinity of the olefin resins and can be solved by allowing fine crystals to be rapidly generated. In order to allow fine crystals to be rapidly generated, for example, a method of adding a nucleator, a crystallization promoter or the like is employed.
Examples of the nucleator that are conventionally used include metal carboxylates such as sodium benzoate, aluminum 4-tert-butylbenzoate, sodium adipate and 2-sodium-bicyclo[2.2.1]heptane-2,3-dicarboxylate; metal phosphates such as sodium-bis(4-tert-butylphenyl)phosphate, sodium-2,2′-methylene-bis(4,6-di-tert-butylphenyl)phosphate and lithium-2,2′-methylene-bis(4,6-di-tert-butylphenyl)phosphate; and compounds having an acetal skeleton, such as dibenzylidene sorbitol, bis(methylbenzylidene)sorbitol and bis(dimethylbenzylidene)sorbitol. These nucleators are disclosed in, for example, Patent Documents 1 to 8.
In cases where the above-described nucleators are directly added to an olefin resin, there are problems in terms of the working environment associated with an addition of powder as well as the ease of handling such as blocking caused by secondary aggregation of the nucleators. Therefore, attempts have been made to prepare a masterbatch of such nucleator and, for example, in Patent Documents 9 and 10, masterbatches for olefin resins are reported. In addition, in Patent Document 11, a masterbatch obtained by melt-kneading a petroleum resin and a nucleator is reported.
Further, Patent Document 12 proposes a method in which propylene is pre-polymerized and then two-step polymerization is performed with an addition of aluminum hydroxy-bis(p-t-butylbenzoate) or sodium benzoate as a nucleator.
As described above, a variety of studies have been conducted on the nucleator to be used in an olefin resin; however, there is still a room for improvement. For example, those nucleators disclosed in Patent Documents 1 to 8 have neither sufficient compatibility with an olefin resin nor sufficient dispersibility in an olefin resin and there is thus a problem that, even when a masterbatch is produced with an addition of the respective nucleators at a high concentration, the expected effects of addition are not exhibited.
Further, in the masterbatches for olefin resins that are disclosed in Patent Documents 9 and 10, the effect of improving the transparency, mechanical strength and the like of an olefin resin is not satisfactory.
The petroleum resin disclosed in Patent Document 11 shows good compatibility with an olefin resin; however, it may impair the intrinsic physical properties of the olefin resin.
Moreover, in a method in which an olefin monomer is polymerized with incorporation of a nucleator thereto at the time of the polymerization, there have been indicated problems that the nucleator reduces the catalytic activity of a polymerization catalyst and causes coloration of the olefin due to interaction with the metal of the polymerization catalyst, and there is also a problem that the selection and management of polymerization conditions are complicated.
The above-described method according to Patent Document 12 aims at uniformly dispersing the nucleator and thereby improving the rigidity of the resulting polymer, and it is a two-step polymerization method in which the nucleator is added after single-step polymerization of propylene. In Patent Document 12, it is disclosed neither that the nucleator may affect the polymerization activity, nor that the nucleator is masked and an adverse effect on the catalytic activity is thereby prevented. In addition, the method according to Patent Document 12 does not show any effect in single-step polymerization where a nucleator is directly brought into contact with a polymerization catalyst. Furthermore, the nucleator described in Patent Document 12 does not dissolve in an organoaluminum compound or an organic solvent and impairs the polymerization activity.
Secondly, olefin-based resins have advantages in their excellent moldability, heat resistance, mechanical properties, low specific gravity and the like and are, therefore, widely utilized in films, sheets and various molded articles (such as structural components). However, since olefin-based resins have a slow crystallization rate when molded, there are drawbacks that the molding cycle properties are poor and that large crystals are generated depending on the progress of crystallization after heat-molding, which leads to insufficient transparency and strength.
It is known, however, that these drawbacks are all attributed to the crystallinity of the olefin-based resins and can be solved by increasing their crystallization temperatures to allow fine crystals to be rapidly generated.
For this purpose, it is known to add a nucleator or a crystallization promoter, and examples thereof that are conventionally used include metal carboxylates such as sodium benzoate, aluminum 4-tert-butylbenzoate, sodium adipate and 2-sodium-bicyclo[2.2.1]heptane-2,3-dicarboxylate; metal phosphates such as sodium-bis(4-tert-butylphenyl)phosphate, sodium-2,2′-methylene-bis(4,6-di-tert-butylphenyl)phosphate and lithium-2,2′-methylene-bis(4,6-di-tert-butylphenyl)phosphate; and compounds having an acetal skeleton, such as dibenzylidene sorbitol, bis(methylbenzylidene)sorbitol and bis(dimethylbenzylidene)sorbitol.
A method for adding these nucleators are widely known and, using a Henschel mixer, a mill roll, a V-blender, a ribbon blender, a kneader blender, a Banbury mixer, a super mixer or the like, an olefin resin and an additive(s) containing a nucleator are mixed, and the resulting mixture is loaded to an extruder and granulated.
Further, Patent Document 12 proposes a method in which aluminum hydroxy-bis(p-t-butylbenzoate) or sodium benzoate is added as a nucleator at the time of polymerizing propylene.
However, in a method in which a nucleator is blended at the time of granulating a polymer, variations may occur in the product physical properties due to defective dispersion of the nucleator. In addition, since the nucleator is powder, there is a problem that the working environment is adversely affected and contaminated due to scattering of the powder and the like during operation. Meanwhile, blending of a nucleator at the time of polymerizing an olefin has a problem that the nucleator inhibits the polymerization activity.
The above-described method according to Patent Document 12 aims at uniformly dispersing the nucleator and thereby improving the rigidity of the resulting polymer, and it is a two-step polymerization method in which the nucleator is added after single-step polymerization of propylene. In Patent Document 12, none of the followings is disclosed: that the nucleator may affect the polymerization activity; that the nucleator is masked and an adverse effect on the catalytic activity is thereby prevented; and that the effect of the nucleator is improved by using an aliphatic metal carboxylate or an alkali metal-containing hydrotalcite in combination. In addition, the method according to Patent Document 12 does not show any effect in a single-step polymerization method in which a nucleator is directly brought into contact with a polymerization catalyst. Furthermore, the nucleator described in Patent Document 12 does not dissolve in an organoaluminum compound or an organic solvent and impairs the polymerization activity.
Thirdly, olefin resins are inexpensive and favorable in various properties such as transparency, heat resistance, surface gloss, oil resistance and mechanical properties; therefore, they are used in a wide range of fields such as industrial materials, automobile materials, home electric appliance materials and packaging materials. Since olefin resins are inexpensive products, they are being studied as an alternative to other resin materials.
Since olefin resins have a slow crystallization rate after being molded, there are drawbacks that the molding cycle is slow and that large crystals are generated depending on the progress of crystallization after heat-molding, which leads to insufficient transparency and strength of the resulting molded article. It is known, however, that these drawbacks are all attributed to the crystallinity of the olefin resins and can be solved by increasing their crystallization temperatures to allow fine crystals to be rapidly generated.
As a method of adding a nucleator before or during polymerization of an olefin monomer, for example, Patent Document 12 proposes a method in which propylene is pre-polymerized and then two-step polymerization is performed with an addition of aluminum hydroxy-bis(p-t-butylbenzoate) or sodium benzoate as a nucleator. Such a method in which a nucleator is added before or during polymerization is advantageous in that a step of blending the nucleator by a melt-kneading process such as extrusion after the polymerization can be omitted; however, there have been indicated problems that the nucleator reduces the catalytic activity of a polymerization catalyst and causes coloration of the resulting polymer due to interaction with the metal of the polymerization catalyst, and there is also a problem that the selection and management of polymerization conditions are complicated.
The above-described method according to Patent Document 12 aims at uniformly dispersing the nucleator and thereby improving the rigidity of the resulting polymer, and it is a two-step polymerization method in which the nucleator is added after single-step polymerization of propylene. In Patent Document 12, it is disclosed neither that the nucleator may affect the polymerization activity, nor that the nucleator is masked and an adverse effect on the catalytic activity is thereby prevented. In addition, the method according to Patent Document 12 does not show any effect in single-step polymerization where a nucleator is directly brought into contact with a polymerization catalyst. Furthermore, the nucleator described in Patent Document 12 does not dissolve in an organoaluminum compound or an organic solvent and impairs the polymerization activity.
Generally, a nucleator itself has poor fluidity and is thus required to be made into a slurry with a solvent; however, since such a nucleator has poor diffusibility in a solution and precipitates over time to cause uneven concentration, there is a problem that olefin polymers polymerized by a batch-type polymerization method have variable nucleating actions and effects.
Fourthly, olefin resins have advantages in their excellent moldability, heat resistance, mechanical properties, low specific gravity and the like and are, therefore, widely utilized in films, sheets and various molded articles (such as structural components). However, since olefin resins have a slow crystallization rate after being molded, there are drawbacks that the molding cycle properties are poor and that large crystals are generated depending on the progress of crystallization after heat-molding, which leads to insufficient transparency and strength.
These drawbacks are all attributed to the crystallinity of the olefin resins and can be solved by increasing their crystallization temperatures to allow fine crystals to be rapidly generated.
For this purpose, it is known to add a nucleator, and examples thereof that are conventionally used include metal carboxylates such as sodium benzoate, aluminum 4-tert-butylbenzoate, sodium adipate and 2-sodium-bicyclo[2.2.1]heptane-2,3-dicarboxylate; metal phosphates such as sodium-bis(4-tert-butylphenyl)phosphate, sodium-2,2′-methylene-bis(4,6-di-tert-butylphenyl)phosphate and lithium-2,2′-methylene-bis(4,6-di-tert-butylphenyl)phosphate; and compounds having an acetal skeleton, such as dibenzylidene sorbitol, bis(methylbenzylidene)sorbitol and bis(dimethylbenzylidene)sorbitol. These nucleators are disclosed in, for example, Patent Documents 1 to 8.
A method for adding these nucleators are widely known and, using a Henschel mixer, a mill roll, a V-blender, a ribbon blender, a kneader blender, a Banbury mixer, a super mixer or the like, an olefin resin and an additive(s) containing a nucleator are mixed, and the resulting mixture is loaded to an extruder and granulated.
Further, Patent Document 12 proposes a method in which propylene is pre-polymerized and then two-step polymerization is performed with an addition of aluminum hydroxy-bis(p-t-butylbenzoate) or sodium benzoate as a nucleator.
However, in a method where a nucleator is blended with an olefin resin, not only variations may occur in the product physical properties due to defective dispersion of the nucleator, but also contamination with a particle product having a large size may occur. In a film material, this causes a defect in the outer appearance of the resulting molded article such as rough surface and, in a fiber material, it causes breakage during molding; therefore, nucleators that can be used in the film and fiber material applications are limited. Further, in cases where a powder nucleator is used, there is a problem that the working environment is adversely affected and contaminated due to scattering of the powder and the like during operation.
Moreover, in a method in which an olefin monomer is polymerized with incorporation of a nucleator thereto at the time of the polymerization, there have been indicated problems that the nucleator reduces the catalytic activity of a polymerization catalyst and causes coloration of the olefin due to interaction with the metal of the polymerization catalyst, and there is also a problem that the selection and management of polymerization conditions are complicated.
The above-described method according to Patent Document 12 aims at uniformly dispersing the nucleator and thereby improving the rigidity of the resulting polymer, and it is a two-step polymerization method in which the nucleator is added after single-step polymerization of propylene. In Patent Document 12, it is disclosed neither that the nucleator may affect the polymerization activity, nor that the nucleator is masked and an adverse effect on the catalytic activity is thereby prevented. In addition, the method according to Patent Document 12 does not show any effect in single-step polymerization where a nucleator is directly brought into contact with a polymerization catalyst. Furthermore, the nucleator described in Patent Document 12 does not dissolve in an organoaluminum compound or an organic solvent and impairs the polymerization activity.
Fifthly, olefin resins are inexpensive and favorable in various properties such as transparency, heat resistance, surface gloss, oil resistance and mechanical properties; therefore, they are used in a wide range of fields such as industrial materials, automobile materials, home electric appliance materials and packaging materials. Since olefin resins are inexpensive products, they are being studied as an alternative to other resin materials and as materials for hygienic applications.
There are various properties required for the use of an olefin resin in a hygienic application. Particularly, the olefin resin, as a container or a packaging material, may come into direct contact with the content; therefore, it is important that the additives to be blended with the olefin resin be non-migratory and that the hygienic property of the molded article be ensured.
Meanwhile, since olefin resins have a slow crystallization rate after being molded, there are drawbacks that the molding cycle is slow and that large crystals are generated depending on the progress of crystallization after heat-molding, which leads to insufficient transparency and strength of the resulting molded article. It is known, however, that these drawbacks are all attributed to the crystallinity of the olefin resins and can be solved by increasing their crystallization temperatures to allow fine crystals to be rapidly generated.
For this purpose, it is known to add a nucleator, and examples thereof that are conventionally used include metal carboxylates such as sodium benzoate, aluminum 4-tert-butylbenzoate, sodium adipate and 2-sodium-bicyclo[2.2.1]heptane-2,3-dicarboxylate; metal phosphates such as sodium-bis(4-tert-butylphenyl)phosphate, sodium-2,2′-methylene-bis(4,6-di-tert-butylphenyl)phosphate and lithium-2,2′-methylene-bis(4,6-di-tert-butylphenyl)phosphate; and compounds having an acetal skeleton, such as dibenzylidene sorbitol, bis(methylbenzylidene)sorbitol and bis(dimethylbenzylidene)sorbitol. These nucleators are disclosed in, for example, Patent Documents 1 to 8.
Among the above-described nucleators, sorbitol derivatives show excellent nucleation effect; however, depending on the application, the use of a sorbitol derivative is limited because it may bleed out of a resin to contaminate a roll during film formation and generates a strong odor during processing. Further, metal salts of aromatic carboxylic acids that are commonly used function as nucleators; however, there are such problems that these metal salts markedly reduce the transparency of an olefin resin and cause generation of a large number of voids when the olefin resin is molded into a film.
As a method of adding a nucleator to an olefin resin, an olefin resin and an additive(s) containing a nucleator or transparentizing agent are mixed using a Henschel mixer, a mill roll, a V-blender, a ribbon blender, a kneader blender, a Banbury mixer, a super mixer or the like and the resulting mixture is loaded to an extruder and granulated.
Further, Patent Document 12 proposes a method in which propylene is pre-polymerized and then two-step polymerization is performed with an addition of aluminum hydroxy-bis(p-t-butylbenzoate) or sodium benzoate as a nucleator.
However, in a method where an olefin polymer and a nucleator are mixed and melt-kneaded, there are problems that the nucleator must be added in an amount more than necessary in order to compensate its poor dispersion in the olefin resin and that the nucleator migrates to the surface of the resulting molded article. Further, in cases where a powder nucleator is used, there is a problem that the working environment is adversely affected and contaminated due to scattering of the powder and the like during operation.
Moreover, although such a method in which a nucleator is blended at the time of polymerizing an olefin monomer is advantageous in that a step of blending the nucleator by a melt-kneading process such as extrusion after the polymerization can be omitted, there have been indicated problems that the nucleator reduces the catalytic activity of a polymerization catalyst and causes coloration of the resulting olefin resin due to interaction with the metal of the polymerization catalyst, and there is also a problem that the selection and management of polymerization conditions are complicated.
The above-described method according to Patent Document 12 aims at uniformly dispersing the nucleator and thereby improving the rigidity of the resulting polymer, and it is a two-step polymerization method in which the nucleator is added after single-step polymerization of propylene. In Patent Document 12, it is disclosed neither that the nucleator may affect the polymerization activity, nor that the nucleator is masked and an adverse effect on the catalytic activity is thereby prevented. In addition, the method according to Patent Document 12 does not show any effect in single-step polymerization where a nucleator is directly brought into contact with a polymerization catalyst. Furthermore, the nucleator described in Patent Document 12 does not dissolve in an organoaluminum compound or an organic solvent and impairs the polymerization activity.
Sixthly, olefin resins are conventionally known as resins that are light-weighted and have excellent mechanical and physical properties, chemical stability and processability and are, therefore, utilized in a wide range of applications in the field of industrial materials, including transportation materials such as containers and pallets; automobile interior and exterior components; large-size containers such as tanks and drums for industrial chemicals and fuels; various bottles for liquid detergents, shampoos, rinses and cooking oils; and home electric appliance materials.
In recent years, production rationalization and cost reduction have been advanced and, in the field of industrial materials, there is an increasing demand for reduction in thickness and weight of the materials and an extremely high-level performance improvement is demanded for olefin resins. In order to respond to these demands, high-performance catalysts having high stereoregularity have been adopted and resin designs have been optimized; however, simple application of these measures has yet to attain sufficient performance and there is a demand for an industrial material having even higher rigidity. Still, for olefin manufacturers, a large-scale facility modification and catalyst changeover cannot be considered advantageous from the standpoints of the cost and profitability.
Conventionally, in the composite material development, attempts have been made to increase the rigidity by adding a filler, for example, an inorganic filler such as talc, to an olefin resin. For instance, this has been done in the large-size blow-molding applications such as structural members including automobile parts where heat resistance and rigidity are required. However, when the amount of an inorganic filler to be added is increased for an improvement of the rigidity, the specific gravity is also increased, so that weight reduction, which is the original purpose, cannot be achieved. Therefore, a material having an improved rigidity whose specific gravity is hardly increased has been strongly desired.
Since olefin resins have a slow crystallization rate after being molded, there are drawbacks that the molding cycle is slow and that large crystals are generated depending on the progress of crystallization after heat-molding, which leads to insufficient transparency and strength of the resulting molded article. It is known, however, that these drawbacks are all attributed to the crystallinity of the olefin resins and can be solved by allowing fine crystals to be rapidly generated at the time of molding the olefin resins.
For this purpose, it is known to add a nucleator, and examples thereof that are conventionally used include metal carboxylates such as sodium benzoate, aluminum 4-tert-butylbenzoate, sodium adipate and 2-sodium-bicyclo[2.2.1]heptane-2,3-dicarboxylate; metal phosphates such as sodium-bis(4-tert-butylphenyl)phosphate, sodium-2,2′-methylene-bis(4,6-di-tert-butylphenyl)phosphate and lithium-2,2′-methylene-bis(4,6-di-tert-butylphenyl)phosphate; and compounds having an acetal skeleton, such as dibenzylidene sorbitol, bis(methylbenzylidene)sorbitol and bis(dimethylbenzylidene)sorbitol. These nucleators are disclosed in, for example, Patent Documents 1 to 8.
As a method of adding the above-described nucleators to an olefin resin, an olefin resin and an additive(s) containing a nucleator are mixed using a Henschel mixer, a mill roll, a V-blender, a ribbon blender, a kneader blender, a Banbury mixer, a super mixer or the like and the resulting mixture is loaded to an extruder and granulated.
Further, Patent Document 12 proposes a method in which propylene is pre-polymerized and then two-step polymerization is performed with an addition of aluminum hydroxy-bis(p-t-butylbenzoate) or sodium benzoate as a nucleator.
However, in a method where an olefin resin and a nucleator are blended by melt-kneading, not only the nucleator must be added in an amount more than necessary in order to compensate its poor dispersion, which is economically disadvantageous, but also there are such problems that the coloration of the nucleator itself causes the resulting molded article to be colored. On the other hand, in cases where a nucleator is added before or during polymerization of an olefin monomer, there is a problem that the nucleator inhibits the polymerization of the olefin monomer.
Moreover, although such a method in which a nucleator is blended at the time of polymerizing an olefin monomer is advantageous in that a step of blending the nucleator by a melt-kneading process such as extrusion after the polymerization can be omitted, there have been indicated problems that the nucleator reduces the catalytic activity of a polymerization catalyst and causes coloration of the resulting olefin resin due to interaction with the metal of the polymerization catalyst, and there is also a problem that the selection and management of polymerization conditions are complicated.
The above-described method according to Patent Document 12 aims at uniformly dispersing the nucleator and thereby improving the rigidity of the resulting polymer, and it is a two-step polymerization method in which the nucleator is added after single-step polymerization of propylene. In Patent Document 12, it is disclosed neither that the nucleator may affect the polymerization activity, nor that the nucleator is masked and an adverse effect on the catalytic activity is thereby prevented. In addition, the method according to Patent Document 12 does not show any effect in single-step polymerization where a nucleator is directly brought into contact with a polymerization catalyst. Furthermore, the nucleator described in Patent Document 12 does not dissolve in an organoaluminum compound or an organic solvent and impairs the polymerization activity.